The electrophotographic (EP) process used in some imaging devices, such as laser printers and copiers, is susceptible to variations due to environmental changes and component life. This variability may have a greater impact on color EP printers because it may cause changes in the toner density of developed images, which in turn causes objectionable color shifts. It is general practice in the industry to incorporate sensors that measure the toner density of test images and provide feedback to the control system for making adjustments to various EP printing process parameters, such as bias voltages and/or laser power. Ideally, these adjustments increase or decrease the amount of toner developed out to the latent image to achieve a desired density.
One common approach to making the adjustments is to measure the reflectivity of a “toner patch” formed inside the printer in order measure the amount of toner being used during the development process. A so-called “toner patch sensor” is used for this purpose, and typically includes an infrared emitter and an associated detector. As can be appreciated, it is advantageous to characterize the toner patch sensor in order to achieve more reliable measurement results so that appropriate adjustments to various EP printing parameters may be made. However, existing methods of characterizing toner patch sensors have proven less than ideal in some circumstances. As such, there remains a need for alternative approaches to characterizing toner patch sensors, and using the corresponding characterization information.